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PROBLEMS with Sigma 50-500mm Zoom Lens on Movie Cameras ??


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#1 George Duncan

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Posted 18 March 2012 - 07:58 AM

At the advise of others, I have purchased a Sigma 50-500mm Zoom Lens for use on our Red-One Camera. It is a beautiful lens in mint, like new condition. This is the model without the OS and with an aperture ring for external control.

I just want to know if any of you who have used this lens on a movie camera, are having the same issues I'm having with it. Therefore, my question is this:

I have owned or used many, many lenses in my life, but never one quite like this. It was obviously designed for still use, but most others made for still cameras do not have these restrictions.

This Sigma lens does NOT hold focus throughout the zoom range. In other words, when focused on the subject at full extension, as you zoom back it goes in and out of focus. No, it is not the back focus adjustment on the camera lens port. As such, this lens can only be used theoretically as a series of fixed lenses and has to be focused at each separate focal length.

If this is normal for this lens, then so be it, and I can live with it. I was hoping I could use it as a zoom lens as well though, but if not, OK. It would be more like having many different lenses all in one.

Another thing I noticed. Most zoom lenses, when an object is too close, you just can't focus on it. But, with this Sigma it "jumps" out of focus when it's past the zoom range it can handle. For instance, it will focus at 300mm, but as soon as you've passed that, to 350mm or beyond, it "immediately" goes super-soft.

Are these things typical of this lens? Is it just the norm because of the design?

If you have any knowledge and experience with this lens I'd appreciate knowing if you have the same issues.

Thanks for your time.

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#2 Stephen Williams

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Posted 18 March 2012 - 03:28 PM

There is a reason that real motion picture lenses are very large, heavy & expensive. You get what you pay for!

At the advise of others, I have purchased a Sigma 50-500mm Zoom Lens for use on our Red-One Camera. It is a beautiful lens in mint, like new condition. This is the model without the OS and with an aperture ring for external control.

I just want to know if any of you who have used this lens on a movie camera, are having the same issues I'm having with it. Therefore, my question is this:

I have owned or used many, many lenses in my life, but never one quite like this. It was obviously designed for still use, but most others made for still cameras do not have these restrictions.

This Sigma lens does NOT hold focus throughout the zoom range. In other words, when focused on the subject at full extension, as you zoom back it goes in and out of focus. No, it is not the back focus adjustment on the camera lens port. As such, this lens can only be used theoretically as a series of fixed lenses and has to be focused at each separate focal length.

If this is normal for this lens, then so be it, and I can live with it. I was hoping I could use it as a zoom lens as well though, but if not, OK. It would be more like having many different lenses all in one.

Another thing I noticed. Most zoom lenses, when an object is too close, you just can't focus on it. But, with this Sigma it "jumps" out of focus when it's past the zoom range it can handle. For instance, it will focus at 300mm, but as soon as you've passed that, to 350mm or beyond, it "immediately" goes super-soft.

Are these things typical of this lens? Is it just the norm because of the design?

If you have any knowledge and experience with this lens I'd appreciate knowing if you have the same issues.

Thanks for your time.

.


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#3 Brian Drysdale

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Posted 19 March 2012 - 03:56 AM

If this is normal for this lens, then so be it, and I can live with it. I was hoping I could use it as a zoom lens as well though, but if not, OK. It would be more like having many different lenses all in one.


It sounds like this lens is a varifocal length lens, which is pretty normal with stills zoom lenses. The zooms used on film and video cameras are parfocal lenses and they hold their focus while you change focal length. Only a few DSLR zooms are parfocal.
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#4 George Duncan

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Posted 19 March 2012 - 06:18 AM

It sounds like this lens is a varifocal length lens, which is pretty normal with stills zoom lenses. The zooms used on film and video cameras are parfocal lenses and they hold their focus while you change focal length. Only a few DSLR zooms are parfocal.


Thanks for your insight, but I knew that already. I was just hoping someone who actually had used this exact lens could tell me that it is normal with the Sigma. As, was said above, that's one of the reasons why pro cine lenses are so expensive in comparison.

Two such people, having experience with this Sigma 50-500mm lens, answered my question on the RedUser Forum, and verified my suspicions. Their lenses do exactly the same thing.

Therefore, my question has been answered, and I appreciate all those who helped.

Thanks.

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#5 Stephen Williams

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Posted 19 March 2012 - 01:04 PM

Thanks for your insight, but I knew that already. I was just hoping someone who actually had used this exact lens could tell me that it is normal with the Sigma. As, was said above, that's one of the reasons why pro cine lenses are so expensive in comparison.

Two such people, having experience with this Sigma 50-500mm lens, answered my question on the RedUser Forum, and verified my suspicions. Their lenses do exactly the same thing.

Therefore, my question has been answered, and I appreciate all those who helped.

Thanks.

.


Of course they don't do what you want, they are cheap STILL camera lenses, they do what they were supposed to do, not more. There is no free lunch with optics.
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#6 rob spence

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Posted 20 March 2012 - 06:58 AM

I did start a list of older parfocal stills zooms...I'll try and dig it out.
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